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June 5, 2017

Living in a city is giving you heart disease, study finds

by Chuck Bednar

Individually, the air pollution and noise pollution typically found in cities have been linked to a variety of health issues, but new research published recently in the European Heart Journal has found that together, they could increase a person’s risk of cardiovascular disease.

Previous research linked urban air pollution to heart disease, stroke, and asthma, as well as noise pollution to increased blood pressure, disturbed sleep and stress, the study authors said in a statement. However, little research had looked at the combined impact of both factors, which are often found together in larger cities, on the overall health of residents.

In the new study, Dr. Yutong Cai from Imperial College London and colleagues analyzed data from 144,000 adults living in Norway and the Netherlands, and compared the amount of traffic-related air and noise pollution exposure they received with blood biological marker levels often used to assess a patient’s risk of contracting heart disease, according to CTV News reports.

Specifically, they tested the subjects’ blood for markers such as C-reactive protein (CRP), a protein which indicates inflammation that can be caused by stress and which, left untreated, can result in heart disease and other health problems. They also tested for blood sugar levels, lipids and triglycerides, each of which has been linked to heart problems and other health issues.

They found evidence indicating that both poor air quality and traffic-related noise pollution are linked to blood biochemistry and that long-term exposure to noise and/or air pollution (much of which is typically produced by automotive traffic) could be associated with increases in each of the aforementioned cardiovascular disease risk factors.

Further research needed to differentiate between air and noise pollution

As part of their research, Dr. Cai’s team developed a statistical model that differentiated between the individual impacts of noise and air pollution. They began by estimating how poor air quality would influence blood sugar, lipid, and CRP levels, while also accounting for age, sex, education and other factors that could influence such biomarkers.

Next, they added noise pollution (defined as noise louder than conversation level, or roughly 60 decibels, according to CTV News) to see if there were any changes in any of the biomarkers. In fact, they found that an increase of just 5 decibels in noise level was linked to a blood sugar level increase of 0.3%.

Even when air pollution was taken into account, the increase persisted, which suggests that noise pollution is an independent cause of increased heart disease risk, the authors said in a statement. Furthermore, they found that a 10 µg/m3 increase in air pollution was linked to a 2.3% increase in blood sugar levels, a 2.6% increase in CRP levels and a 10% spike in triglycerides, even when noise pollution was not factored into the equation.

“When studying road traffic noise, it can be difficult to differentiate between air and noise pollution, as they often go hand in hand,” Dr. Cal explained. “Our findings contribute to the strong scientific evidence that both air pollution and traffic noise are bad for our health, although to further differentiate between air and noise pollution will need more work.”

“Either way, the message is clear: public health policy must act on these environmental stressors to protect our health and wellbeing,” he added. However, as study co-author Dr. Susan Hodgson, also a researcher working at Imperial College London, noted, “Our study moves us a step closer to understanding the link between air and noise pollution exposure and cardiovascular disease, evidence which to date is very limited.”